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United States Patent |
5,599,254
|
Tomisawa
,   et al.
|
February 4, 1997
|
Method and apparatus for diagnosing a fault in a lock-up mechanism of a
torque converter fitted to an automatic transmission
Abstract
A slip condition of a torque converter is learned at a predetermined
operating condition with a lock-up mechanism disengaged, and a diagnosis
condition (for example a start time or judgement level of the fault
diagnosis) used in diagnosing a fault in the lock-up mechanism on the
basis of slip conditions of the torque converter which change after issue
of a disengage command to the lock-up mechanism, is corrected in
accordance with the learned result. As a result, the diagnosis condition
which is conventionally set assuming a maximum viscosity for the operating
fluid, can be changed to correspond to the actual viscosity of the
operating fluid being used. Hence, the time delay from issue of a
disengage command to the lock-up mechanism until starting fault diagnosis
can be reduced, so that it is possible to diagnose if normal lock-up
mechanism disengagement is being made at a response speed which follows
the demands for rapid lock-up mechanism disengagement under operating
conditions including acceleration and deceleration operating conditions
such as encountered with city driving and the like.
Inventors:
|
Tomisawa; Naoki (Atsugi, JP);
Yoshizawa; Keita (Atsugi, JP)
|
Assignee:
|
Unisia Jecs Corporation (Atsugi, JP)
|
Appl. No.:
|
385710 |
Filed:
|
February 8, 1995 |
Foreign Application Priority Data
Current U.S. Class: |
477/176; 192/3.3; 192/3.31 |
Intern'l Class: |
F16D 033/00; B60K 041/02; F16H 061/14 |
Field of Search: |
192/3.29,3.3,3.31
74/731.1
477/176
|
References Cited
U.S. Patent Documents
4700819 | Oct., 1987 | Nishikawa et al. | 192/3.
|
4724939 | Feb., 1988 | Lockhart et al. | 192/3.
|
4953677 | Sep., 1990 | Aoki et al. | 192/3.
|
5121820 | Jun., 1992 | Brown et al. | 192/3.
|
5160002 | Nov., 1992 | Suzuki | 192/3.
|
5190128 | Mar., 1993 | Iizuka | 192/3.
|
5332073 | Jul., 1994 | Iizuka | 192/3.
|
Foreign Patent Documents |
2-195072 | Aug., 1990 | JP | 192/3.
|
Primary Examiner: Luong; Vinh T.
Assistant Examiner: Jensen; Nathan O.
Attorney, Agent or Firm: Foley & Lardner
Claims
We claim:
1. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the method comprising the steps of:
detecting a rotational speed of the input shaft of the torque converter;
detecting a rotational speed of the output shaft of the torque converter;
detecting a slip condition of the torque converter based on the detected
input shaft rotational speed and the detected output shaft rotational
speed;
diagnosing a fault in the lock-up mechanism by comparing a slip condition
of the torque converter after lapse of a predetermined time from issuance
of a disengage command to the lock-up mechanism with a previously
determined judgment value;
learning a slip condition of the torque converter at a predetermined
operating condition with the lock-up mechanism disengaged; and
correcting the predetermined time as a diagnosis condition of the fault
diagnosis step in accordance with the learned result of the slip
condition.
2. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 1, wherein the
slip condition learning step is carrier out after lapse of a predetermined
time from issuance of a disengage command to the lock-up mechanism.
3. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the method comprising the steps of:
detecting a rotational speed of the input shaft of the torque converter;
detecting a rotational speed of the output shaft of the torque converter;
detecting a slip condition of the torque converter based on the detected
input shaft rotational speed and the detected output shaft rotational
speed;
diagnosing a fault in the lock-up mechanism by comparing a slip condition
of the torque converter after lapse of a predetermined time from issuance
of a disengage command to the lock-up mechanism with a previously
determined judgment value;
learning a slip condition of the torque converter at a predetermined
operating condition with the lock-up mechanism disengaged; and
correcting the predetermined time and the judgment value as diagnosis
conditions of the fault diagnosis step in accordance with the learned
result of the slip condition.
4. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 3, wherein the
slip condition learning step is carrier out after lapse of a predetermined
time from issuance of a disengage command to the lock-up mechanism.
5. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the method comprising the steps of:
detecting a rotational speed of the input shaft of the torque converter;
detecting a rotational speed of the output shaft of the torque converter;
detecting a slip condition of the torque converter based on the detected
input shaft rotational speed and the detected output shaft rotational
speed;
diagnosing a fault in the lock-up mechanism by comparing the required time
from issuance of a disengage command to the lock-up mechanism until a slip
condition of the torque converter reaches a previously determined judgment
value, with a previously determined judgment time;
learning a slip condition of the torque converter at a predetermined
operating condition with the lock-up mechanism disengaged; and
correcting the judgment time as a diagnosis condition of the fault
diagnosis step in accordance with the learned result of the slip
condition.
6. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 5, wherein the
slip condition learning step is carrier out after lapse of a predetermined
time from issuance of a disengage command to the lock-up mechanism.
7. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the method comprising the steps of:
detecting a rotational speed of the input shaft of the torque converter;
detecting a rotational speed of the output shaft of the torque converter;
detecting a slip condition of the torque converter based on the detected
input shaft rotational speed and the detected output shaft rotational
speed;
diagnosing a fault in the lock-up mechanism by comparing the required time
from issuance of a disengage command to the lock-up mechanism until a slip
condition of the torque converter reaches a previously determined judgment
value, with a previously determined judgment time;
learning a slip condition of the torque converter at a predetermined
operating condition with the lock-up mechanism disengaged; and
correcting the judgment value as a diagnosis condition of the fault
diagnosis step in accordance with the learned result of the slip
condition.
8. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 7, wherein the
slip condition learning step is carrier out after lapse of a predetermined
time from issuance of a disengage command to the lock-up mechanism.
9. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the method comprising the steps of:
detecting a rotational speed of the input shaft of the torque converter;
detecting a rotational speed of the output shaft of the torque converter;
detecting a slip condition of the torque converter based on the detected
input shaft rotational speed and the detected output shaft rotational
speed;
diagnosing a fault in the lock-up mechanism by comparing the required time
from issuance of a disengage command to the lock-up mechanism until a slip
condition of the torque converter reaches a previously determined judgment
value, with a previously determined judgment time;
learning a slip condition of the torque converter at a predetermined
operating condition With the lock-up mechanism disengaged; and
correcting the judgment time and the judgment value as diagnosis conditions
of the fault diagnosis step in accordance with the learned result of the
slip condition.
10. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 9, wherein the
slip condition learning step is carrier out after lapse of a predetermined
time from issuance of a disengage command to the lock-up mechanism.
11. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the method comprising the steps of:
detecting a rotational speed of the input shaft of the torque converter;
detecting a rotational speed of the output shaft of the torque converter;
detecting a slip condition of the torque converter based on the detected
input shaft rotational speed and the detected output shaft rotational
speed;
diagnosing a fault in the lock-up mechanism by comparing a change factor
for the slip conditions of the torque converter, which slip conditions
change after issuance of a disengage command to the lock-up mechanism,
with a previously determined judgment value;
learning a slip condition of the torque converter at a predetermined
operating condition with the lock-up mechanism disengaged; and
correcting the judgment value as a diagnosis condition of the fault
diagnosis step in accordance with the learned result of the slip
condition.
12. A method of diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 11, wherein the
slip condition learning step is carrier out after lapse of a predetermined
time from issuance of a disengage command to the lock-up mechanism.
13. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the apparatus comprising:
an input shaft rotational speed detecting means for detecting a rotational
speed of the input shaft of the torque converter;
an output shaft rotational speed detecting means for detecting a rotational
speed of the output shaft of the torque converter;
a slip detecting means for detecting a slip condition of the torque
converter based on the detected input shaft rotational speed and the
detected output shaft rotational speed;
a fault diagnosing means for diagnosing a fault in the lock-up mechanism by
comparing a slip condition of the torque converter after lapse of a
predetermined time from issuance of a disengage command to the lock-up
mechanism with a previously determined judgment value;
a slip condition learning means for learning a slip condition of the torque
converter at a predetermined operating condition with the lock-up
mechanism disengaged; and
a diagnosis condition correction means for correcting the predetermined
time as a diagnosis condition of the fault diagnosis step in accordance
with the learned result of the slip condition.
14. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 13, wherein the
slip condition learning is carrier out after lapse of a predetermined time
from issuance of a disengage command to the lock-up mechanism.
15. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the apparatus comprising:
an input shaft rotational speed detecting means for detecting a rotational
speed of the input shaft of the torque converter;
an output shaft rotational speed detecting means for detecting a rotational
speed of the output shaft of the torque converter;
a slip detecting means for detecting a slip condition of the torque
converter based on the detected input shaft rotational speed and the
detected output shaft rotational speed;
a fault diagnosing means for diagnosing a fault in the lock-up mechanism by
comparing a slip condition of the torque converter after lapse of a
predetermined time from issuance of a disengage command to the lock-up
mechanism with a previously determined judgment value;
a slip condition learning means for learning a slip condition of the torque
converter at a predetermined operating condition with the lock-up
mechanism disengaged; and
a diagnosis condition correction means for correcting the predetermined
time and judgment value as diagnosis conditions of the fault diagnosis
step in accordance with the learned result of the slip condition.
16. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 15, wherein the
slip condition learning is carrier out after lapse of a predetermined time
from issuance of a disengage command to the lock-up mechanism.
17. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the apparatus comprising:
an input shaft rotational speed detecting means for detecting a rotational
speed of the input shaft of the torque converter;
an output shaft rotational speed detecting means for detecting a rotational
speed of the output shaft of the torque converter;
a slip detecting means for detecting a slip condition of the torque
converter based on the detected input shaft rotational speed and the
detected output shaft rotational speed;
a fault diagnosing means for diagnosing a fault in the lock-up mechanism by
comparing the required time from issuance of a disengage command to the
lock-up mechanism until a slip condition of the torque converter reaches a
previously determined judgment value, with a previously determined
judgment time;
a slip condition learning means for learning a slip condition of the torque
converter at a predetermined operating condition with the lock-up
mechanism disengaged; and
a diagnosis condition correction means for correcting the judgment time as
a diagnosis condition of the fault diagnosis step in accordance with the
learned result of the slip condition.
18. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 17, wherein the
slip condition learning is carrier out after lapse of a predetermined time
from issuance of a disengage command to the lock-up mechanism.
19. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the apparatus comprising:
an input shaft rotational speed detecting means for detecting a rotational
speed of the input shaft of the torque converter;
an output shaft rotational speed detecting means for detecting a rotational
speed of the output shaft of the torque converter;
a slip detecting means for detecting a slip condition of the torque
converter based on the detected input shaft rotational speed and the
detected output shaft rotational speed;
a fault diagnosing means for diagnosing a fault in the lock-up mechanism by
comparing the required time from issuance of a disengage command to the
lock-up mechanism until a slip condition of the torque converter reaches a
previously determined judgment value, with a previously determined
judgment time;
a slip condition learning means for learning a slip condition of the torque
converter at a predetermined operating condition with the lock-up
mechanism disengaged; and
a diagnosis condition correction means for correcting the judgment value as
a diagnosis condition of the fault diagnosis step in accordance with the
learned result of the slip condition.
20. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 19, wherein the
slip condition learning is carrier out after lapse of a predetermined time
from issuance of a disengage command to the lock-up mechanism.
21. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the apparatus comprising:
an input shaft rotational speed detecting means for detecting a rotational
speed of the input shaft of the torque converter;
an output shaft rotational speed detecting means for detecting a rotational
speed of the output shaft of the torque converter;
a slip detecting means for detecting a slip condition of the torque
converter based on the detected input shaft rotational speed and the
detected output shaft rotational speed;
a fault diagnosing means for diagnosing a fault in the lock-up mechanism by
comparing the required time from issuance of a disengage command to the
lock-up mechanism until a slip condition of the torque converter reaches a
previously determined judgment value, with a previously determined
judgment time;
a slip condition learning means for learning a slip condition of the torque
converter at a predetermined operating condition with the lock-up
mechanism disengaged; and
a diagnosis condition correction means for correcting the judgment time and
value as diagnosis conditions of the fault diagnosis step in accordance
with the learned result of the slip condition.
22. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 21, wherein the
slip condition learning is carrier out after lapse of a predetermined time
from issuance of a disengage command to the lock-up mechanism.
23. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission, the torque converter being
connected to an output shaft of a vehicle engine, wherein the lock-up
mechanism is provided for mechanically coupling input and output shafts of
the torque converter, the apparatus comprising:
an input shaft rotational speed detecting means for detecting a rotational
speed of the input shaft of the torque converter;
an output shaft rotational speed detecting means for detecting a rotational
speed of the output shaft of the torque converter;
a slip detecting means for detecting a slip condition of the torque
converter based on the detected input shaft rotational speed and the
detected output shaft rotational speed;
a fault diagnosing means for diagnosing a fault in the lock-up mechanism by
comparing a change factor for the slip conditions of the torque converter,
which slip conditions change after issuance of a disengage command to the
lock-up mechanism, with a previously determined judgment value;
a slip condition learning means for learning a slip condition of the torque
converter at a predetermined operating condition with the lock-up
mechanism disengaged; and
a diagnosis condition correction means for correcting the judgment value as
a diagnosis condition of the fault diagnosis step in accordance with the
learned result of the slip condition.
24. An apparatus for diagnosing a fault in a lock-up mechanism of a torque
converter in an automatic transmission according to claim 23, wherein the
slip condition learning is carrier out after lapse of a predetermined time
from issuance of a disengage command to the lock-up mechanism.
Description
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for diagnosing a
fault in a lock-up mechanism of a torque converter provided in a vehicle
automatic transmission. More particularly the present invention relates to
method and apparatus which can diagnose whether or not rapid disengagement
of a lock-up mechanism is functioning normally under operating conditions
including acceleration and deceleration such as encountered with city
driving and the like.
DESCRIPTION OF THE RELATED ART
Heretofore, in general with electronically controlled automatic
transmissions connected by way of a torque converter to an internal
combustion engine, under predetermined conditions a lock-up clutch is
engaged so that the output shaft of the engine (ie., the torque converter
input shaft) and the input shaft of the automatic transmission (ie., the
torque converter output shaft) are integrally connected. As a result the
difference in rotational speed between the engine and the automatic
transmission becomes zero, so that the engine output is effectively
transferred to the automatic transmission, thereby improving fuel
consumption and exhaust composition.
However, if an abnormality occurs in the lock-up clutch itself, or in a
lock-up solenoid valve which supplies and shuts off hydraulic pressure
supplied from a hydraulic mechanism to engage or disengage the lock-up
clutch, and control system etc. (also referred to hereunder as the lock-up
mechanism), so that the lock-up clutch cannot be engaged as required in
spite of operating under predetermined conditions for engagement, then a
rotational speed difference will occur between the engine and the
automatic transmission, so that the engine output cannot be effectively
transferred to the automatic transmission. As a result more engine output
than normal is required, causing a deterioration in fuel consumption and
exhaust composition, and a drop in acceleration performance.
Alternatively, if the engagement of the lock-up clutch cannot be released,
then various types of problems arise such as an increase in speed change
shook, engine stall, and difficulty in starting, causing a loss in vehicle
drivability. Moreover, since the rotational speed of the engine will drop
more than necessary with influence from the drive system, then with
subsequent acceleration, the acceleration required to match the demand of
the driver will be lacking by a recovery amount for the engine rotational
speed. Accelerator operation must therefore be increased to compensate for
this amount, causing a deterioration in fuel consumption and exhaust
composition.
Such unfavourable conditions can be detected based for example on the ratio
of the rotational speeds of the input and output shafts of the torque
converter at the time of engagement and disengagement of the lock-up
clutch (for example, on the slip ratio=N2/N1, where N1 is the input shaft
rotational speed (ie., the engine rotational speed) and N2 is the output
shaft rotational speed), or on the ratio of the input shaft rotational
speed N1 and the vehicle speed VSP (for example, on the slip
ratio=VSP/(k.times.N1), where k is a constant based for example on the
final speed reduction ratio and the tire diameter). That is, unfavourable
conditions of the lock-up mechanism can be diagnosed to occur when, in
spite of an engage command, the slip ratio is large, or in spite of a
disengage command, the ratio of the input and output shaft rotational
speeds or the slip ratio is small.
With regards to diagnosing whether or not the lock-up clutch has been
disengaged, then as shown in FIG. 17, since the viscosity of the operating
fluid inside the torque converter differs for example, due to
deterioration with time, difference in temperature conditions, or due to
different properties of the operating fluid itself, the time until the
slip ratio becomes stable will differ due to the difference in the
viscosity. Therefore, it has heretofore been necessary to delay the start
period for the diagnosis until a predetermined time has elapsed from issue
of the disengage command to the lock-up clutch. With normal operation of
the lock-up mechanism, this delay is made comparatively long to ensure
that the slip ratio (judgement slice level) is definitely above a
predetermined value irrespective of changes in the viscosity of the
operating fluid.
Consequently, with the conventional arrangement, since the start time for
fault diagnosis related to lock-up clutch disengagement is delayed, then
even if rapid lock-up clutch disengagement is not being carried out as
required under operating conditions including acceleration and
deceleration such as encountered with city driving and the like, due for
example to a drop in reduction rate of the hydraulic pressure supplied to
the lock-up clutch, or a drop in the opening or closing speed of the
lock-up solenoid valve, this cannot be detected. That is to say, the
situation is such that deterioration in fuel consumption, exhaust
composition, and drivability etc. caused by the abnormality of rapid
disengagement of the lock-up clutch cannot be addressed.
SUMMARY OF THE INVENTION
The present invention takes into consideration the above situation with the
conventional arrangement, with the object of providing a fault diagnosis
method and apparatus for a lock-up mechanism, which can diagnose to a high
accuracy whether or not rapid lock-up mechanism disengagement is being
carried out as required under operating conditions including acceleration
and deceleration, so as to keep to a minimum the undesirable conditions
such as a deterioration in fuel consumption, exhaust composition, and
vehicle drivability which occur with city driving and the like. It is a
further object of the present invention to achieve this with a simple
construction and improved diagnosis accuracy.
In view of the above objects, the method and apparatus according to the
present invention for diagnosing a fault in a lock-up mechanism of a
torque converter fitted to an automatic transmission, involves; an input
shaft rotational speed detecting step and device A for detecting a
rotational speed of an input shaft of the torque converter, an output
shaft rotational speed detecting step and device B for detecting a
rotational speed of an output shaft of the torque converter, a slip
condition detecting step and device C for detecting a slip condition of
the torque converter based on the torque converter input shaft rotational
speed and output shaft rotational speed, a fault diagnosis step and device
D for diagnosing a fault in the lock-up mechanism on the basis of a slip
condition of the torque converter during change after issue of a disengage
command to the lock-up mechanism, detected by the slip condition detecting
step and device C, a slip condition learning step and device E for
learning a slip condition of the torque converter at a predetermined
operating condition with the lock-up mechanism disengaged, and a diagnosis
condition correction step and device F for correcting a diagnosis
condition of the fault diagnosis step and device D in accordance with the
learned result of the slip condition.
With such a construction, a slip condition of the torque converter is
learned at a predetermined operating condition with the lock-up mechanism
disengaged, and a diagnosis condition used in diagnosing a fault in the
lock-up mechanism on the basis of slip conditions of the torque converter
which change after issue of the disengage command to the lock-up
mechanism, is corrected in accordance with the learned result (that is,
with consideration of the viscosity of the operating fluid in the torque
converter). Therefore, with the present invention, the diagnosis condition
which was conventionally set assuming a maximum viscosity for the
operating fluid, can be set and changed to correspond to the actual
viscosity of the operating fluid being used. Hence, the time delay from
issue of a disengage command to the lock-up mechanism until starting fault
diagnosis can be reduced, so that it is possible to diagnose if normal
lock-up mechanism disengagement is being made at a response speed which
follows the demands for rapid lock-up mechanism disengagement under
operating conditions including acceleration and deceleration operating
conditions such as encountered with city driving and the like.
Accordingly, poor response characteristics of the lock-up mechanism can be
detected, so that this can be brought to the attention of the driver for
appropriate action. The deterioration in fuel consumption, exhaust
composition, and drivability and the like, attributable to poor lock-up
mechanism response characteristics under operating conditions such as city
driving can thus be significantly reduced.
When the construction is such that the fault diagnosis step and device D
diagnoses a fault in the lock-up mechanism by comparing a slip condition
of the torque converter after lapse of a predetermined time from issue of
a disengage command to the lock-up mechanism, with a previously determined
judgement value, then the predetermined time as the diagnosis condition
may be corrected by the diagnosis condition correction step and device F.
More specifically, a slip condition of the torque converter is learned at
a predetermined operating condition with the lock-up mechanism disengaged,
and the predetermined time from issue of the disengage command to the
lock-up mechanism until start of the fault diagnosis, that it to say the
diagnosis start time is corrected in accordance with the learned result
(for example, in accordance with a change in viscosity of the operating
fluid in the torque converter) (refer to FIG. 6). Hence, the start time of
the fault diagnosis which is set at a greatly delayed setting in
consideration of the maximum viscosity, can be set and changed by means of
a simple construction so as to correspond to the actual viscosity of the
operating fluid being used. The diagnosis start time can thus be advanced
corresponding to the viscosity of the operating fluid, so that it is
possible to diagnose if normal lock-up mechanism disengagement is being
made at a response speed which follows the demands for rapid lock-up
mechanism disengagement such as encountered with city driving and the
like. Accordingly, poor response characteristics of the lock-up mechanism
occurring in such driving conditions can be detected, so that this can be
brought to the attention of the driver for appropriate action. The
deterioration in fuel consumption, exhaust composition, and drivability
and the like, under operating conditions such as city driving can thus be
significantly reduced.
Moreover, when the construction is such that the fault diagnosis step and
device D diagnoses a fault in the lock-up mechanism by comparing a slip
condition of the torque converter after lapse of a predetermined time from
issue of a disengage command to the lock-up mechanism, with a previously
determined judgement value, then the previously determined judgement value
as the diagnosis condition may be corrected by the diagnosis condition
correction step and device F. More specifically, a slip condition of the
torque converter is learned, and the judgement value for judging fault
diagnosis by comparison with actual slip conditions is corrected in
accordance with the learned result (for example, in accordance with a
change in viscosity of the operating fluid in the torque converter) (refer
to FIG. 8). If the judgement value is changed in this way in accordance
with the learned result, then as with the previous construction, diagnosis
of faults in the lock-up mechanism can be made with good response
characteristics, corresponding to the actual viscosity of the operating
fluid being used. Accordingly it is possible to diagnose if normal lock-up
mechanism disengagement is being made at a response speed which follows
the demands for rapid lock-up mechanism disengagement such as encountered
with city driving and the like. The deterioration in fuel consumption,
exhaust composition, and drivability and the like, under operating
conditions such as city driving can thus be significantly reduced.
When the construction is such that the fault diagnosis step and device D
diagnoses a fault in the lock-up mechanism by comparing a slip condition
of the torque converter after lapse of a predetermined time from issue of
a disengage command to the lock-up mechanism, with a previously determined
judgement value, then both the predetermined time and the judgement value
as the diagnosis conditions may be corrected by the diagnosis condition
correction step and device F. More specially, a slip condition of the
torque converter is learned, and the predetermined time from issue of the
disengage command to the lock-up mechanism until start of the fault
diagnosis, and the judgement value for judging fault diagnosis by
comparison with actual slip conditions are both corrected in accordance
with the learned result (refer to FIG. 5). As a result, it is possible to
diagnose, while maintaining high judgement accuracy, if normal lock-up
mechanism disengagement is being made at a response speed which follows
the demands for rapid lock-up mechanism disengagement such as encountered
with city driving and the like.
When the construction is such that the fault diagnosis step and device D
diagnoses a fault in the lock-up mechanism by comparing a required time
from issue of a disengage command to the lock-up mechanism until a slip
condition of the torque converter reaches a previously determined
judgement value, with a previously determined judgement time, then the
judgement time as the diagnosis condition may be corrected by the
diagnosis condition correction step and device F. More specifically, a
slip condition of the torque converter is learned, and the judgement time
for comparison with the required time from issue of the disengage command
to the lock-up mechanism until the slip condition reaches the previously
determined judgement value, is corrected in accordance with the learned
result (refer to FIG. 10). Hence, the start time of the fault diagnosis
which is set at a greatly delayed setting in consideration of the maximum
viscosity, can be set and changed so as to correspond to the actual
viscosity of the operating fluid being used. As a result, it is possible
to diagnose if normal lock-up mechanism disengagement is being made at a
response speed which follows the demands for rapid lock-up mechanism
disengagement such as encountered with city driving and the like.
Accordingly, the time delay from issue of a disengage command to the
lock-up mechanism until starting fault diagnosis can be reduced
corresponding to the actual viscosity of the operating fluid being used.
The deterioration in fuel consumption, exhaust composition, and
drivability and the like, occurring under operating conditions such as
city driving can thus be significantly reduced.
Moreover, when the construction is such that the fault diagnosis step and
device D diagnoses a fault in the lock-up mechanism by comparing a
required time from issue of a disengage command to the lock-up mechanism
until a slip condition of the torque converter reaches a previously
determined judgement value, with a previously determined judgement time,
then the judgement value as the diagnosis condition may be corrected by
the diagnosis condition correction step and device F. More specifically, a
slip condition of the torque converter is learned at a predetermined
operating condition with the lock-up mechanism disengaged, and the
judgement value is corrected in accordance with the learned result, that
is to say, in accordance with a change in viscosity of the operating fluid
in the torque converter (refer to FIG. 12). If the judgement value is
changed in this way in accordance with the learned result, then even with
an advanced fault diagnosis start time, faults in the lock-up mechanism
can still be adequately diagnosed. Therefore, the fault diagnosis start
time is advanced so that it is possible to diagnose if normal lock-up
mechanism disengagement is being made at a response speed which follows
the demands for rapid lock-up mechanism disengagement such as encountered
with city driving and the like. The deterioration in fuel consumption,
exhaust composition, and drivability and the like, under operating
conditions such as city driving can thus be significantly reduced.
Furthermore, when the construction is such that the fault diagnosis step
and device D diagnoses a fault in the lock-up mechanism by comparing a
required time from issue of a disengage command to the lock-up mechanism
until a slip condition of the torque converter reaches a previously
determined judgement value, with a previously determined judgement time,
then both the judgement time and the judgement value as the diagnosis
conditions may be corrected by the diagnosis condition correction step and
device F. More specifically, when such an arrangement as mentioned above
is provided for the fault diagnosis step and device, a slip condition of
the torque converter is learned at a predetermined operating condition
with the lock-up mechanism disengaged, and the judgement time and the
judgement value are both corrected in accordance with the learned result
(refer to FIG. 14). As a result, it is possible to diagnose, while
maintaining high judgement accuracy, if normal lock-up mechanism
disengagement is being made at a response speed which follows the demands
for rapid lock-up mechanism disengagement such as encountered with city
driving and the like.
Additionally, when the construction is such that the fault diagnosis step
and device D diagnoses a fault in the lock-up mechanism by comparing a
change factor for the slip conditions of the torque converter which change
after issue of the disengage command to the lock-up mechanism, with a
previously determined judgement value, then the judgement value as the
diagnosis condition may be corrected by the diagnosis condition correction
step and device F. More specifically, a slip condition of the torque
converter is learned, and the judgement value is corrected in accordance
with the learned result (refer to FIG. 15). With such a construction,
since a slip condition change factor is detected, then fault diagnosis can
be carried out in a very short time after issue of the disengage command.
Consequently, it is possible to diagnose, if normal lock-up mechanism
disengagement is being made at high response speeds which follow the
demands for very rapid lock-up mechanism disengagement in city driving and
the like. The deterioration in fuel consumption, exhaust composition, and
drivability and the like, under operating conditions such as city driving
can thus be kept to a minimum.
Regarding the slip condition learning step and device E, preferably this
involves learning a slip condition of the torque converter at a
predetermined operating condition after lapse of a predetermined time from
issue of a disengage command to the lock-up mechanism. That is to say, it
is preferable to simply detect the disengage condition of the lock-up
mechanism with a simple construction using the elapsed time from issue of
a disengage command to the lock-up mechanism.
Other objects and aspects of the present invention will become apparent
from the following description of embodiments of the invention given in
conjunction with the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of the present invention;
FIG. 2 is a schematic diagram showing the overall construction of
embodiments of the present invention:
FIG. 3 is a flow chart for explaining a slip ratio learning routine in the
present embodiments;
FIG. 4 is a flow chart for explaining a fault diagnosis control routine for
the lock-up mechanism in a first embodiment;
FIG. 5 is a time chart for explaining operations in the first embodiment;
FIG. 6 is a time chart for explaining operations in a fault diagnosis step
and device of a second embodiment;
FIG. 7 is a flow chart for explaining a fault diagnosis control routine of
a lock-up mechanism in the fault diagnosis step and device of the second
embodiment;
FIG. 8 is a time chart for explaining operations in a fault diagnosis step
and device of a third embodiment;
FIG. 9 is a flow chart for explaining a fault diagnosis control routine of
a lock-up mechanism in the fault diagnosis step and device of the third
embodiment;
FIG. 10 is a time chart for explaining operations in a fault diagnosis step
and device of a fourth embodiment;
FIG. 11 is a flow chart for explaining a fault diagnosis control routine of
a lock-up mechanism in the fault diagnosis step and device of the fourth
embodiment;
FIG. 12 is a time chart for explaining operations in a fault diagnosis step
and device of a fifth embodiment;
FIG. 13 is a flow chart for explaining a fault diagnosis control routine of
a lock-up mechanism in the fault diagnosis step and device of the fifth
embodiment;
FIG. 14 is a time chart for explaining operations in a fault diagnosis step
and device of a sixth embodiment;
FIG. 15 is a time chart for explaining operations in a fault diagnosis step
and device of a seventh embodiment;
FIG. 16 is a flow chart for explaining a fault diagnosis control routine of
a lock-up mechanism in a fault diagnosis step and device of the seventh
embodiment; and
FIG. 17 is a time chart for explaining problems with conventional methods
and apparatus, showing the change of a slip ratio with change in viscosity
of an operating fluid.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of fault diagnosis methods and apparatus according to the
present invention for diagnosing a fault in a lock-up mechanism of a
torque converter fitted to an automatic transmission are shown in FIG. 2
through FIG. 16.
As shown in FIG. 2, an engine 1 draws in air from an air cleaner 2 by way
of an intake duct 3, an air flow meter 4 for detecting an intake air
quantity Q, a throttle valve 5 operated by an accelerator pedal (not shown
in the figure), and an intake manifold 6. The throttle valve 5 is provided
with a throttle sensor 7 for detecting a throttle valve opening (TVO)
thereof. An output signal from the throttle sensor 7 corresponding to the
throttle valve opening TVO is input to a control unit 50. Also provided on
the throttle valve 5 is an idle switch 8 for generating an 0N signal
(which is also input to the control unit 50) when the throttle valve 5 is
fully closed.
Fuel injection valves 9 are provided for each cylinder in respective branch
portions of the intake manifold 6. The fuel injection valves 9 are
electromagnetic type fuel injection valves which open with power to a
solenoid and close with power shut-off. The fuel injection valves 9 are
driven open in response to a drive pulse signal from the control unit 50
(to be described later) so that fuel pressurized by a fuel pump, and
controlled to a predetermined pressure by means of a pressure regulator,
is injected into the engine 1. Ignition plugs (not shown in the figure)
are provided for each combustion chamber of the engine 1, for igniting a
mixture therein based on an ignition signal from the control unit 50.
An output shaft of the engine 1 is integrally connected to an input shaft
11 of a torque converter generally indicated by arrow 10, so as to
rotatingly drive a pump impeller 12 which is also integrally connected to
the input shaft 11. The motive force of the engine 1 is transferred to an
output shaft 15 of the torque converter 10 through the medium of an
operating fluid 13 contained in the torque converter 10, by rotational
drive of a turbine runner 14 which is integrally connected to the output
shaft 15. The motive force transferred to the output shaft 15 is input to
an automatic transmission 17 by way of an input shaft 16 connected to the
output shaft 15.
The motive force input in this way to the automatic transmission 17, is
first changed by the mechanism inside the automatic transmission 17 to a
predetermined speed based on a signal from the control unit 50, and is
then output from an output shaft 18. The motive force output from the
output shaft 18 is transferred to drive wheels 26 by way of, for example,
a propeller shaft (not shown in the figure), a differential gear 24 and an
axle shaft 25.
The torque converter 10 is provided with a lock-up clutch 19 which
mechanically connects the input shaft 11 to the output shaft 15. Hydraulic
pressure is supplied to or shut off from the lock-up clutch 19 by an
opening or closing operation of a lock-up solenoid 20 disposed in a
hydraulic mechanism (not shown in the figure). As a result, a lock-up
piston 21 is moved either towards the left in FIG. 2 to press against a
friction plate 22 provided integrally with the input shaft 11 and engage
therewith, or towards the right in FIG. 2 to separate from the friction
plate 22.
While the above construction is such that the lock-up solenoid 20 opens a
valve to engage the lock-up clutch 19, and closes the valve to separate
the lock-up clutch 19, it is also possible for the alternative arrangement
wherein the lock-up solenoid 20 opens the valve to separate the lock-up
clutch 19, and closes the valve to engage the lock-up clutch 19. The
lock-up solenoid 20 performs the opening and closing operation under
predetermined conditions based on a drive signal generated from the
control unit 50. The lock-up clutch 19, lock-up solenoid 20, hydraulic
mechanism, and control unit 50 etc. constitute the lock-up mechanism of
the present invention. While the present embodiment has been described for
a friction type lock-up mechanism, it is of course possible to use an
electromagnetic type lock-up mechanism.
A crank angle sensor 23 is incorporated into a distributor (not shown) of
the engine 1. To determined the engine rotational speed N1, the control
unit 50 either counts over a fixed period unit crank angle signals output
from the crank angle sensor 23 in synchronous with the engine rotation, or
measures the period of a reference crank angle signal. The rotational
speed N1 of the engine 1 can also be directly detected from the rotational
speed of the input shaft 11 of the torque converter 10. The crank angle
sensor 23 constitutes the torque converter input shaft rotational speed
detecting device of the present invention.
A vehicle speed sensor 27 which detects rotational speed of the axle shaft
25, and detects vehicle speed (VSP) based on the speed change step of the
automatic transmission 17 is also provided. The vehicle speed sensor 27
constitutes the torque converter output shaft rotational speed detecting
device of the present invention. The rotational speed of the axle shaft 25
may be detected for example using a gear mechanism.
The control unit 50 incorporates a microcomputer having for example, a CPU,
ROM, RAM, A/D converter and input/output interface. This receives input
signals from the various sensors, and controls the fuel injection amount
of the fuel injection valves 9 as described in outline below.
More specifically, the control unit 50 computes the basic fuel injection
quantity (engine load) Tp from the intake air quantity Q detected by the
air flow meter 4, and the engine rotational speed N1 obtained by counting
the pulse signals from the crank angle sensor 23 over a fixed period
(Tp=c.times.Q/N1, where c is a constant), and outputs, as a drive pulse
signal to the fuel injection valves 9, a final fuel injection quantity Te
obtained by correcting the basic fuel injection quantity Tp with various
correction coefficients (for example an air-fuel ratio feedback correction
coefficient, a water temperature correction coefficient, a learning
correction coefficient, and a load correction coefficient).
The control unit 50 also receives signals from the throttle sensor 7 and
the like, and the vehicle speed sensor 27, and looks up a speed change
control map based for example on previously stored throttle valve openings
TVO (or engine loads Tp), and the vehicle speed (VSP), to effect control
of the automatic transmission.
Referring now to the flow chart of FIG. 3, a slip condition learning
routine carried out in the control unit 50, and required for diagnosing
whether or not the lock-up mechanism is operating with the required
response speed, will now be explained. The slip condition learning routine
detects for example viscosity changes accompanying deterioration with age
of the operating fluid 13, viscosity change with temperature, or viscosity
change at the time of changing to an operating fluid 13 of different
properties (viscosity index and the like). The slip condition learning
routine constitutes the slip condition learning device of the present
invention.
In step 1 (with step indicated by S in the figures) it is judged if a
disengage signal for the lock-up clutch 19 (that is, a disengage command
to the lock-up mechanism) is being sent to the lock,up solenoid 20. If so
(YES), control proceeds to step 2, while if not (NO), control proceeds to
step 7 where an elapsed time TM from issue of the disengage signal is
cleared, and the learning routine is then terminated.
In step 2, it is judged if the elapsed time from issue of the disengage
signal has attained the predetermined time TM shown in FIG. 5, sufficient
for the slip ratio a.sub.n (to be described later ) to be completely
stable in spite of viscosity changes of the operating fluid 13. If so, the
control proceeds to step 3, while if not, the routine is repeated until
the elapsed time from issue of the disengage signal becomes the
predetermined time TM. The predetermined time TM assuming the operating
fluid 13 to be one of maximum viscosity, can be a predetermined time for
the slip ratio to become stable.
In step 3, it is judged from the current engine rotational speed N1 (that
is, the rotational speed of the input shaft 11 of the torque converter 10)
and from the engine load Tp, if the existing operating conditions are
within the predetermined operating range (operating range for producing
the predetermined slip ratio). If so, control proceeds to step 4, while if
not, the learning routine is terminated.
In step 4, the slip ratio a.sub.n (=VSP/(k.times.N1) where k is a
constant)is computed. This can of course be obtained from the ratio of N2
to N1 after converting the vehicle speed VSP into the torque converter
output shaft rotational speed N2. Moreover, a rotation sensor may be
provided on the output shaft 15, so that the torque converter output shaft
rotational speed N2 can be obtained directly. However, if, as with the
present embodiments, the signals from the crank angle sensor 23 and the
vehicle speed sensor 27 are used, then additional sensors need not be
provided, this minimizing costs.
Step 4 constitutes the slip condition detection device of the present
invention.
In step 5, a weighted mean value "a" of the slip ratio a.sub.n
(=((n-1).times.a+a.sub.n)/ n) is computed. Then, in step 6, the computed
weighted mean value "a" is updated in the memory of the control unit 50.
The above is the learning routine for the slip ratio.
Referring now to the flow chart of FIG. 4 showing a first embodiment, a
lock-up mechanism fault diagnosis routine carried out in the control unit
50, for diagnosing whether or not the lock-up mechanism is operating with
the required response speed, will now be explained. The control unit 50
with this function, thus functions as the fault diagnosis device of the
present invention.
In step 11, depending on the weighted mean value "a", a diagnosis start
time t.sub.d from issue of a disengage signal until start of the
diagnosis, and a judgement slice level a.sub.L for the diagnosis, are
retrieved from a map or the like which has been verified for example, by
prior experiment and stored in the control unit 50. The reason for
changing the diagnosis start time td and the judgement slice level a.sub.L
together, is so that the diagnosis start time td can be shortened while
maintaining a high judgement accuracy (refer to FIG. 5). However, it will
be understood, as mentioned later, that it is possible to change only the
diagnosis start time td (refer to FIG. 6), or with the diagnosis start
time td set short, it is possible to change only the diagnosis judgement
slice level a.sub.L corresponding to the viscosity of the operating fluid
13 (refer to FIG. 8).
Step 11 constitutes the diagnosis condition correction device of the
present invention.
In step 12, it is judged if a disengage signal for the lock-up clutch 19
(that is, a disengage command to the lock-up mechanism) is being sent to
the lock-up solenoid 20. If so, control proceeds to step 13 to continue
fault diagnosis, while if not, control proceeds to step 17 where an
elapsed time TM2 from issue of the disengage signal is cleared, and the
routine is then terminated.
In step 13, the elapsed time TM2 from issue of the disengage signal is
compared with the time td newly set in step 11 for the time until
diagnosis starts. If TM2.gtoreq.td, control proceeds to step 14, while if
TM2<td, the routine repeats until TM2.gtoreq.td.
In step 14, the judgement slice level a.sub.L set in step 11, is compared
with the current slip ratio a.sub.n (=vehicle speed VSP/(k.times.N1),
where k is a constant). If a.sub.L .ltoreq.a.sub.n, control proceeds to
step 15, while if a.sub.L >a.sub.n, control proceeds to step 16.
In step 15, since the current slip ratio a.sub.n is above the predetermined
slip ratio a.sub.L, it is judged that the lock-up mechanism has disengaged
with a normal response speed, and is thus diagnosed as operating normally.
On the other hand, in step 16, since the current slip ratio a.sub.n is less
than the predetermined slice level a.sub.L, it is judged that the lock-up
mechanism has disengaged at a response speed slower than the normal
response speed. For example it is judged that a restriction in the
hydraulic supply system to the lock-up solenoid 20 is above a prescribed
value, or the opening and closing speed of the lock-up solenoid 20 itself
has dropped more than a predetermined value, so that the lock-up mechanism
is diagnosed to be faulty. In this case, a warning device such as a light
provided in the driving cab may come on, to bring this to the attention of
the driver for appropriate action.
In this way, with the present embodiment, since the fault diagnosis start
time td, and/or the judgement level a.sub.L are changed in accordance with
the learned value "a" of the slip ratio a.sub.n, that is to say in
accordance with the change in viscosity of the operating fluid 13, then
the large delay for the fault diagnosis start time which is conventionally
set assuming a maximum viscosity for the operating fluid 13 is not
necessary. Hence fault diagnosis of the lock-up mechanism can be carried
out at a response speed based on the change of the viscosity of the
operating fluid 13.
More specifically, since a drop in the reduction rate of the hydraulic
pressure supplied to the lock-up clutch 19, due to the amount of
restriction in the hydraulic supply system to the lock-up solenoid 20, or
a drop in the transitional operating response speed of the lock-up
mechanism due for example to a drop in the opening or closing speed of the
lock-up solenoid 20 itself, can be detected to a high accuracy, then it is
possible to diagnose to a high accuracy whether or not rapid lock-up
mechanism disengagement occurring for example in city driving and the
like, is being carried out as required. Furthermore, by bringing such a
fault to the attention of the driver for appropriate action, deterioration
in fuel consumption, exhaust composition, and drivability and the like,
under operating conditions such as city driving can be significantly
reduced.
With the first embodiment, in the diagnosis routine, the fault diagnosis
start time td, and the judgement level a.sub.L are both changed in
accordance with the learned value "a" of the slip ration a.sub.n, that is
to say in accordance with the change in viscosity of the operating fluid
13, so that the diagnosis start time td can be shortened while maintaining
a high judgement accuracy (corresponding to claim however, it will be
understood as shown in FIG. 6 corresponding to a second embodiment, that
it is possible to change only the diagnosis start time td, with the
judgement level a.sub.L as a constant. In this case also, since the
diagnosis can be started at a diagnosis start time matched to the normally
used viscosity of the operating fluid 13, and since the diagnosis start
time td set in the conventional manner in consideration of a maximum
viscosity can be shortened, then it is possible to diagnose whether or not
the operation can follow the demands for rapid lock-up mechanism
disengagement, while also simplifying the control logic (corresponding to
claim 2. Refer to the flow chart of FIG. 7).
Moreover, as shown in FIG. 8 corresponding to a third embodiment, if the
judgement slice level a.sub.L is changed corresponding to the viscosity of
the operating fluid 13, then even if the diagnosis start time td is
shortened beforehand, fault diagnosis can still be made to a high
accuracy. Therefore, the delay in the diagnosis start time conventionally
set in consideration of the maximum viscosity is not necessary.
Accordingly, since the diagnosis start time td can be significantly
shortened, then it is possible to diagnose whether or not the operation
can follow the demands for rapid lock-up mechanism disengagement, while
also simplifying the control logic (corresponding to claim 3. Refer to the
flow chart of FIG. 9).
As shown in FIG. 10 corresponding to a fourth embodiment, when the
construction is such that the fault diagnosis device diagnoses a fault in
the lock-up mechanism by comparing a required time T from issue of a
disengage command to the lock-up mechanism until a slip ration a.sub.n of
the torque converter 10 reaches a previously determined judgement slice
level a.sub.L, with a previously determined judgement time TL, then the
judgement time TL is corrected, in accordance with the learned result "a"
of the slip ration a.sub.n, to T1, T2 corresponding to the change in the
viscosity of the operating fluid 13. Then even with a construction wherein
the required time td (expressed respectively as tdl, td2 in FIG. 10) from
initial issue of the disengage signal to the lock-up mechanism until the
time when the existing slip ration a.sub.n reaches the judgement slice
level a.sub.L is detected, and respectively compared with the judgement
times T1, T2 (the invention disclosed in claim 5), since the diagnosis can
be started at a diagnosis start time matched to the normally used
viscosity of the operating fluid 13, and since the judgement time TL set
in the conventional manner in consideration of a maximum viscosity can be
effectively shortened, then it is still possible to diagnose whether or
not the operation can follow the demands for rapid lock-up mechanism
disengagement (refer to the flow chart of FIG. 11 ).
As shown in FIG. 12 corresponding to a fifth embodiment, in the case where
the fault diagnosis device has the abovementioned construction, and the
judgement slice level a.sub.L is corrected, in accordance with the learned
result "a" of the slip ration a.sub.n, to A1, A2, A3 corresponding to the
change in the viscosity of the operating fluid 13, then if the
construction is such that the required time td from initial issue of the
disengage signal to the lock-up mechanism until the time when the existing
slip ration a.sub.n reaches the judgement slice levels A1, A2, A3 is
detected, and the required time td and a previously set judgement time TL
are compared (corresponding to claim 6), then even if the judgement time
TL is previously set shorter, fault diagnosis can still be carried out at
a high accuracy corresponding to the viscosity of the operating fluid 13.
Therefore, the delay in the diagnosis start time conventionally set in
consideration of a maximum viscosity is not necessary. Accordingly, since
the diagnosis start time tdl can be significantly shortened, then it is
possible to diagnose whether or not the operation can follow the demands
for rapid lock-up mechanism disengagement, while also simplifying the
control logic (Refer to the flow chart of FIG. 13).
As shown in FIG. 14 corresponding to a sixth embodiment, in the case where
the fault diagnosis device has the abovementioned construction, and the
judgement slice level a.sub.L is corrected, in accordance with the learned
result "a" of the slip ration a.sub.n, to A1, A2, A3 corresponding to the
change in the viscosity of the operating fluid 13, then if the
construction is such that the required times tdl, td2, td3 from initial
issue of the disengage signal to the lock-up mechanism until the time when
the existing slip ration a.sub.n reaches the judgement slice levels A1,
A2, A3 are detected, and respectively compared with judgement times T1,
T2, T3 previously set to correspond to the required times (corresponding
to claim 7), then it will be evident, as with the beforementioned flow
chart of FIG. 4, that the diagnosis start time td can be shortened, while
maintaining a high diagnosis accuracy.
As shown in FIG. 15 corresponding to a seventh embodiment, a change factor
a (=(a.sub.n -a.sub.n- 1)/(t.sub.n -t.sub.n- 1), where t represents time,
and n, n-1 are subscripts for current and previous) of the slip ration
a.sub.n occurring after the disengage command to the lock-up clutch 19,
can be detected as the diagnosis condition occurring after issue of the
disengage command to the lock-up clutch 19. The detected change factor a
can then be compared with a judgement value a.sub.m which is suitably
modified to correspond to the learning result, to diagnose a fault in the
lock-up mechanism. In this case, compared to the previous embodiments,
since the change factor a can be detected immediately after issue of the
disengage command, then fault diagnosis can be carried out in a very short
time (corresponding to claim 8. Refer to the flow chart of FIG. 16).
Accordingly, it is possible to diagnose, if normal lock-up mechanism
disengagement is being made at high response speeds which follow a demand
for very rapid lock-up mechanism disengagement. The deterioration in fuel
consumption, exhaust composition, and drivability and the like, under
operating conditions such as city driving can thus be kept to a minimum.
When the learning value "a" of the slip ration a.sub.n obtained in the
present embodiments becomes greater than a predetermined value, then it is
judged that the operating fluid 13 has reached its useful limit, and this
can be indicated by a warning light to tell the driver to change the
operating fluid 13.
Moreover, the temperature of the operating fluid 13 can be detected, and
the viscosity of the operating fluid 13 which bears a mutual relation to
the temperature, as well as an appropriate value for the learned value "a"
of the slip ration a.sub.n can be estimated to some degree (this can be to
a higher accuracy if viscosity deterioration due to accumulated use time
or accumulated running distance is taken into consideration). It then
becomes possible to modify the elapsed time td and the judgement slice
level a.sub.L in accordance with the estimated viscosity or the
appropriate value for the learned value "a". In this case, since the slip
ratio need not be learnt, then even though the engine operation may not
protrude into the learning region so that learning is not possible, the
abovementioned lock-up mechanism fault diagnosis can be quickly started,
based on the presumed viscosity of the operating fluid 13 within a
comparatively short time immediately after starting driving.
In the above embodiments, the learned value "a" of the slip ration a.sub.n
can be obtained for each operating condition, and treated by averaging and
the like to reduce the learning error.
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